Area Forecast Discussion
Issued by NWS Rapid City, SD

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FXUS63 KUNR 220138
AFDUNR

Area Forecast Discussion For Western SD and Northeastern WY
National Weather Service Rapid City SD
738 PM MDT Thu Mar 21 2024

.UPDATE...
Issued at 736 PM MDT Thu Mar 21 2024

Some minor tweaks to PoPs and QPF this evening as good forcing and
steep lapse rates along the boundary has alowed for some light to
moderate precipitation rates as it moves through the CWA.

&&

.KEY MESSAGES...
220 PM MDT Thu Mar 21 2024

-Unsettled/active weather pattern in store through much of the
 next week

-Heavy snow increasingly likely across northwest through central
 SD Sat night through Sunday as a strong storm system crosses the
 region

&&

.DISCUSSION...(This Evening Through Thursday)
Issued at 220 PM MDT Thu Mar 21 2024

Active amplified flow will support increasing chances for precip,
along with accumulating snow for parts of the area. Frontal
boundary stalled across the area with a mid level impulse
progressing across the region. Steep mid level lapse rates are
supporting convective snow showers across NW SD where temps have
been holding into the 20s, while across the far SW temps have
warmed into the 50s under partly sunny skies. Impulse will
progress across the region this evening, with light snow accums
expected under the heavier and more persistent snow showers, most
of which will be found across NW SD with added forcing from FGEN.
As the impulse shifts across the region tonight, snow shower
chances will spread across most of the area, with light accums
(generally and inch or less possible, mainly in the northern BH).
Cold front will settle back south Friday, with slight chances for
light snow shifting northeast through the day. The next impulse
will shift the front back north aloft as a warm front with a
decent FGEN band expected across the NE third of the FA by Friday
night. Accums of 1-2 inches will be possible on most of the SD
plains, mainly from Buffalo to Winner and east. Slightly warmer
conds expected Sat most places, esp the SW. Rain/snow showers will
be possible again by Sat afternoon in the warm sector ahead of
the next impulse, which will be the much stronger western CONUS
trough. As this system ejects on the plains, a cold front will
slide through the region Sat night with LSA increasing as well as
chances for rain/snow. Models continue to focus the best chances
for snow across NW SD and central/eastern SD where several inches
of snow will be possible trough Sunday. Further west, dry slotting
and localized downsloping off the BH will highly limit snow
amounts in NE WY, SW SD, and on the plains SE of the Black Hills.
There remains some uncertainty wrt to where the main deformation
zone will develop, which will be driven by the upper impulse
track. But confidence that most of the SD plains to see snow
accums are high. In addition, winds will increase as the sfc low
deepens, supporting blowing/drifting snow, esp toward central SD.
Snow will end Monday, with very cold temps settling into the
region. Highs will only be in the teens/20s Monday, with a warming
trend through mid next week. Flow over the eastern Pac will
continue to support an active pattern next week, with more chances
for rain/snow later in the week.

&&

.AVIATION...(For the 00Z TAFS Through 00Z Friday Evening)
Issued At 523 PM MDT Thu Mar 21 2024

MVFR conditions will be possible across NW SD as light to moderate
rain/snow moves across the this evening. VFR conditions will
prevail over the rest of the area through this evening, with
chances for rain/snow showers. MVFR/local IFR ceilings will
spread south from MT/ND in the overnight hours, covering much of
the forecast area, and improving late Friday morning and
afternoon.

&&

.UNR WATCHES/WARNINGS/ADVISORIES...
SD...None.
WY...None.
&&

$$

Update...Dye
DISCUSSION/KEY MESSAGES...JC
AVIATION...Dye


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